In recent years, there has been demand for thinner and smaller electric devices such as liquid crystal display devices.
A semiconductor device adopting a film carrier tape (hereinafter referred to as a film carrier-type semiconductor device) is beginning to be used mainly for a liquid crystal driver. A package of the film carrier-type semiconductor device is generally referred to as TCP (Tape Carrier Package).
FIG. 16 and FIG. 17 illustrate a conventional film carrier-type semiconductor device (TCP) wherein a semiconductor chip 110 is mounted on a device hall 135 which is provided on a predetermined position on an insulating base material tape 134. Note that, in the following explanation, the film carrier-type semiconductor device will be referred to simply as a semiconductor device.
The semiconductor device has an arrangement wherein the semiconductor chip 110 is electrically connected to inner leads 102 via bumps 111 from the side opposite to the insulating base material tape 134 surface on which conductive wiring is provided. The inner leads 102 are provided so as to project into the device hall 135. The conductive wiring is composed of (1) outer leads 103 and 104 and (2) the inner leads 102 provided on the insulating base material tape 134. The bumps 111 are made of gold (Au).
On a wiring pattern composed of the inner leads 102 and the outer leads 103 and 104, there is provided an organic insulating film 101 having a predetermined pattern. Also, resin 122 is provided by potting around portions where the semiconductor chip 110 and the inner leads 102 are combined with each other.
The semiconductor device having the described arrangement is said to have a normal bonding structure wherein the semiconductor chip 110 is connected to the inner leads 102 from the side opposite to the insulating base material tape 134 surface on which the conductive wiring is provided.
The following will explain a manufacturing method of the semiconductor device having the described arrangement.
First, a wafer is attached to a dicing sheet so as to be diced into individual semiconductor chips. Here, the thickness of the wafer is 0.625 mm if the diameter of the wafer is 6 inch, or 0.725 mm if the diameter of the wafer is 8 inch.
Secondly, in an inner lead bonding (ILB) step, the semiconductor chip is combined with a film carrier.
Generally, an ILB device employed in the ILB step includes a mechanism for transporting the film carrier, a mechanism for aligning (1) the electrode of the semiconductor chip and (2) the inner leads so as to induce bonding, and a mechanism for storing the film carrier which has been subjected to the bonding.
Specifically, in the ILB step, upon setting the film carrier to the ILB device, the film carrier is transported piece by piece so as to connect the semiconductor chip to the inner leads. Note that, the semiconductor chip is aligned by two alignment-use inner leads of the film carrier before the connection takes place.
The semiconductor chip is set to the ILB device while attached to a dicing sheet. Each semiconductor chip thus set is lifted from below by a metal needle and is absorbed by an absorbing collet so as to be fixed on a bonding stage of the ILB device.
Thirdly, the semiconductor chip thus fixed on the bonding stage is aligned in accordance with the aluminium pattern formed on the semiconductor chip. Namely, in the ILB device, the bonding stage fixed on the semiconductor chip, rather than the film carrier, is moved so as to precisely align the inner leads of the film carrier and the electrode of the semiconductor chip.
Fourthly, after the semiconductor chip is aligned, a bonding tool applies pressure and heat to the semiconductor chip through the inner leads of the film carrier. This results in the formation of an eutectic composed of (1) a bump made of gold (Au) provided on the semiconductor chip and (2) tin (Sn) of the inner leads of the film carrier, thereby combining the semiconductor chip with the film carrier. Note that, the heat applied by the bonding tool has a temperature of substantially 500.degree. C. which is applied for substantially 1 second. Also, a cycle of inner-lead-bonding of one semiconductor chip is substantially 4 to 10 seconds.
After completion of the ILB, liquid resin (protective resin) is applied to the surface of and around the semiconductor chip. The liquid resin thus applied to the surface of the semiconductor passes through the space between the semiconductor chip and the device hall of the film carrier and reaches the sides of the semiconductor chip so as to form meniscus (resin 122 having a semilunar shape on the sides of the semiconductor chip 110 in FIG. 16) on a polyimide insulating base material tape of the film carrier and the semiconductor chip. Note that, the liquid resin is made of thermosetting resin which is completely cured in an oven for substantially 2 to 10 hours after it is prebaked in a curing furnace.
After sealing the protective resin, the semiconductor device is marked. The marking is made by a laser or with ink on the surface of the organic insulating film provided on a resin surface, the bottom surface of the semiconductor chip, a film carrier base material, and the film carrier.
The semiconductor device manufactured in the described manner is sorted out in the testing step so as to distinguish defective products from nondefective products.
Next, the following will explain a structure and a manufacturing method of the film carrier employed in the semiconductor device.
As shown in FIG. 17 and FIG. 18(i), the film carrier has an arrangement wherein the inner leads 102 and the outer leads 103 and 104 (conductive wiring) are provided so as to be patterned on the insulating base material tape 134 provided with the device hall 135 on its predetermined position, and the portion of each lead which is not covered with the organic insulating film 101 is covered with tin-plate 130.
The following will explain the manufacturing method of the film carrier having the described arrangement.
First, a slit is provided on a tape base material made of polyimide in accordance with the semiconductor chip to be combined with. Here, the tape base material has a width of substantially 500 mm, and the slit has a width of either 35 mm, 48 mm, or 70 mm. Then, the surface of the tape base material thus prepared is laminated with a bonding agent, thereby forming the insulating base material tape 134 of FIG. 18(a).
Secondly, as shown in FIG. 18(b), the insulating base material tape 134 is perforated by molding. The perforation is required for the device hall 135, the slit (not shown), and the film transport.
Thirdly, as shown in FIG. 18(c), an electrolytic copper foil 138 is laminate-bonded with the insulating base material tape 134 by the bonding agent laminated on the surface of the insulating base material tape 134. Here, the electrolytic copper foil 138 is available in various thicknesses, i.e.,18 .mu.m, 24 .mu.m, and 36 .mu.m, etc. from which an appropriate thickness is selected according to the pitch of the inner leads 102.
Fourthly, as shown in FIG. 18(d), a photoresist 139 is applied to the surface of the electrolytic copper foil 138 provided on the insulating base material tape 134, and an etching resist 109 is printed with respect to the device hall 135 from the side opposite to the surface of the insulating base material tape 134 on which the electrolytic copper foil 138 is provided so as to form a unidirectional wiring pattern on the surface of the insulating base material tape 134.
Then, the surface of the electrolytic copper foil 138 of FIG. 18(d) provided on the insulating base material tape 134 is processed so as to remove an oxidation film or other films. Thereafter, after applying the photoresist 139 so as to form a predetermined pattern, as shown in FIG. 18(e), the photoresist 139 is exposed and developed, thereby forming an etching mask 139a.
Fifth, as shown in FIG. 18(f), the electrolytic copper foil 138 is etched with stannic chloride so as to form a wiring pattern 138a. Then, an alkaline solution is applied so as to simultaneously remove (1) the photoresist 139 provided on the wiring pattern 138a made of the electrolytic copper foil 138 and (2) the etching resist 109 so as to expose the wiring pattern 138a, as shown in FIG. 18(g).
Sixth, as shown in FIG. 18(h), the organic insulating film 101 is printed on the wiring pattern made of the electrolytic copper foil 138 except portions of the outer lead 103 of the input side, the outer lead 104 of the output side, and the inner leads 102. Here, the organic insulating film 101 acts as a solder resist.
Finally, as shown in FIG. 18(i), after printing the organic insulating film 101, the respective exposed portions of the outer leads 103 and 104 and the inner leads 102 of the wiring pattern 138a, are non-electroplated with tin so as to form the tin-plate 130 having a thickness in a range of 0.2 .mu.m to 0.6 .mu.m. Then, after the tin metal plating, the film carrier having the described arrangement is cured for 1 hour to 3 hours at a temperature in a range of 110.degree. C., to 140.degree. C. as a preventative measure against generation of whisker.
The film carrier manufactured in the described manner is shipped after performing an open/short test.
Alternatively, other than the described semiconductor device having the normal bonding structure, the semiconductor devices shown in FIG. 19 and FIG. 20 are available as a semiconductor device adopting the film carrier. The semiconductor devices of FIG. 19 and FIG. 20 have an arrangement wherein the semiconductor chip 110 is provided on the side where the wiring pattern of the insulating base material tape 134 is formed. A semiconductor device having this arrangement is said to have a reverse bonding structure. In FIG. 19 and FIG. 20, members having the same functions as the members shown in FIG. 16 are given the same reference numerals, and detailed explanations thereof are omitted here.
In the semiconductor device of FIG. 20, after completion of the ILB, low-viscous resin (under fill resin) 124 is injected into a portion where the semiconductor chip 110 and the insulating base material tape 134 are combined with each other so as to be cured, thereby sealing the protective resin.
Resin stoppers 137 are provided on the organic insulating film 101 (1) provided between the outer lead 103 and the inner leads 102 provided on the insulating base material tape 134 and (2) provided between the outer lead 104 and the inner leads 102 provided on the insulating base material tape 134. The resin stoppers 137 are provided so as to prevent the low-viscous resin 124 from flowing out.
According to the afore-mentioned conventional semiconductor device provided with the device hall and the overhanging inner leads (see FIG. 16, FIG. 17, and FIG. 19), the inner leads 102 overhang the device hall 135, and the resin 122 is provided around the device hall 135 so as to maintain a mechanical strength. However, this arrangement has a drawback in that the thickness of the resin 122 is in a range of only 100 .mu.m to 300 .mu.m even on the semiconductor device 110. This reduces the mechanical strength, and therefore presents a problem that the semiconductor device 110 may be broken only with a small external force.
The conventional semiconductor devices having the described arrangements have several drawbacks.
(1) In the above-mentioned semiconductor device, the inner leads 102 project into the device hall 135 of the insulating base material tape 134 (film carrier). Thus, in the case where the inner leads 102 have a fine pitch so as to make the gap between inner leads 102 have a length of not more than 50 .mu.m, the thickness of the inner leads 102 becomes thin and the width of the inner leads narrows as well. This reduces the strength of the inner leads 102, and therefore presents a problem that the inner leads 102 are susceptible to deformation.
(2) In the above-mentioned semiconductor device, in the ILB, since the bonding tool which has been heated is pressed against the inner leads which have been plated with tin, the bonding tool is stained as the tin adheres to the bonding tool. In this case, the bonding tool is cleaned by polishing thereof with a ceramic abrasive plate. However, because the bonding tool is required to be cleaned at least once while manufacturing 100 semiconductor devices, the throughput of the ILB step cannot be improved. Further, repeated cleaning of the bonding tool scratches the surface of the bonding, which causes inadequate results to occur in the ILB step.
(3) Normally, the ILB completes with the formation of the eutectic composed of the bump on the semiconductor chip and the tin plated on the inner leads. Therefore, when the thickness of the tin plated on the inner leads side is thick and the temperature in the ILB step rises above a required temperature, the size of the eutectic composed of the gold and the tin increases greatly, which substantially lowers the strength of the inner leads after the ILB.
(4) In the ILB step, a CCD (Charge Coupled Device) camera recognizes a portion where the semiconductor chip and the film carrier are combined with each other. However, because the bonding tool is heated to substantially 500.degree. C., a flame is generated when the CCD camera recognizes the portion where the semiconductor chip and the film carrier are combined with each other. This lowers the recognition accuracy. Further, thermal expansion causes the insulating base material tape to bend, thereby lowering the accuracy of aligning the semiconductor chip and the film carrier.
(5) The semiconductor chip after the ILB is fixed by the inner leads of the film carrier. However, because the inner leads are made of copper foil having a thickness of 18 .mu.m to 36 .mu.m, the strength thereof is extremely low. Thus, if handled improperly, such a problem as deformation or breakage of the inner leads may occur.
(6) After the ILB, the resin-sealing is made by potting of liquid resin made of the thermosetting resin with respect to the portion where the semiconductor chip and the film carrier are combined with each other. However, in general, the viscosity of the liquid resin tends to vary depending on the manufacturing lot. This presents a problem that the thicknesses of the resin on the semiconductor chip vary. For example, when the thickness of the resin film on the semiconductor chip is thin, the moisture resistance lowers in this thin portion. Further, if a foreign conductive object adheres to this thin portion on the semiconductor chip, failure such as an electrical leaking might result.
(7) For post curing, it is required to cure the liquid resin (sealant) in an oven for additional 2 hours to 10 hours after it is prebaked. For this reason, it takes time to produce a semiconductor device whose semiconductor chip and film carrier are combined with each other, and in which the combined portion is sealed by the liquid resin (hereinafter referred to as an assembly).
Also, the post curing of the resin causes copper (material for a conductive wiring pattern) to diffuse into the tin plated on the outer lead. This makes it difficult to solder the assembly to an electric device such as a liquid crystal module.
(8) According to the conventional semiconductor device, it is required for the inner leads to have a bend having a length of substantially 100 .mu.m (see FIG. 16) so as to prevent the breakage of the inner leads due to the expansion of the film carrier. For this reason, a large portion of the semiconductor device protrudes from the device hall of the film carrier, thereby increasing the thickness of the semiconductor device.
(9) In a film carrier-type semiconductor device having a long narrow semiconductor chip, the semiconductor chip may crack due to a small external force.
(10) In the conventional film carrier-type semiconductor device, when mounting, the interface between the polyimide base material of the film carrier and the resin (sealant) is susceptible to a crack or a peeling. This lowers the moisture resistance of a product employing the above-mentioned semiconductor device.
(11) In the conventional film carrier-type semiconductor device, the bumps on the semiconductor device can only be provided peripherally in accordance with design the inner leads of the film carrier. This lowers flexibility of the semiconductor device.
(12) A conventional semiconductor device provided with no device hall (see FIG. 20) has an arrangement wherein the semiconductor chip is connected face down to the inner leads from above the conductive wiring pattern formed on the insulating base material tape. For this reason, compared to the semiconductor device of FIG. 16 and FIG. 19 provided with the device hall, higher strength can be achieved. However, when mounting the semiconductor device of a reverse bonding type on the liquid crystal module of FIG. 3 (explanatory drawing of the present invention), the semiconductor chip contacts a glass epoxy substrate or a liquid crystal panel connected to the conductive wiring pattern. Thus, when mounting the semiconductor device of a reverse bonding type on the liquid crystal module, it is required to provide a space in the liquid crystal module so as to prevent the semiconductor chip from contacting the glass epoxy substrate or the liquid crystal panel. However, in this case, the semiconductor device cannot be made thinner. The same problem is also presented in the semiconductor device of a reverse bonding type shown in FIG. 19.